According to John Holdren, director of the White House's Office of Science and Technology Policy, Earth is still vulnerable to a potential catastrophic asteroid strike and NASA has substantial progress in finding that asteroids can be a threat.

"We are not fully prepared, but we are on a trajectory to get much more so," Holdren said yesterday, Sept. 14 at NASA's Goddard Space Flight Center, during a dialogue of the agency's planned Asteroid Redirect Mission (ARM).

Holdren named the February 2013 meteor explosion over the city of Chelyabinsk in Russia and 1908 Tunguska airburst and these are reasons to take asteroid threat seriously.

Chelyabinsk was struck bya 65-feet or 20 meter-wide object resulting in 1,200 injured people. Whereas the Tunguska event was even more destructive. The space rock that hit Tunguska was about 130 feet wide or 40 meters and exploded over a mostly unpopulated region in Siberia. It flattened about 800 square miles or 2,070 square kilometers of the forest. Both of the events shocked the world.

"We know that this does happen." Said Holdren. "Strikes such as what happened in Chelyabinsk are thought to happen once in every hundred years, while Tunguska is regarded as a once in 1,000 years event."

The ARM can educate us, Holdren added. By late 2021, NASA is aiming to launch a robotic probe toward an asteroid near Earth. It is a 1,300 feet wide asteroid called 2008 EV5. After reaching the asteroid, the space probe will investigate the potential of a deflection strategy known as the "enhanced gravity tractor."

The agency officials said that the probe will return to Earth, eventually placing the boulder in orbit around the moon. Astronauts aboard NASA's Orion Space Capsule will then visit the purloined rock in the mid-2020s.

The ARM costs $1.25 billion. It is expected to help researchers learn more about asteroids and the resources they possess, demonstrate many of the technologies needed to get astronauts to Mars, help the agency practice human operations in deep space and improve the skills that will be needed to deflect a potentially dangerous asteroid someday.